We are studying the mechanism of growth control in cell culture in a two phase research program combining (1) somatic cell genetics of SV40-transformed mouse cells in culture and (2) biochemistry of the control of RNA and DNA synthesis in cell-free systems. From a diploid transformed mouse line, SVT2, which carries 1-2 copies of the whole SV40 genome, we have isolated hypotetraploid lines which still carry at least large portions of the viral genome but are not phenotypically transformed, by several criteria. Expression of viral T-antigen in at least one of these lines appears to depend on the growth state of the cells. In preliminary work 2 lines express tumor-specific transplantation antigen. We plan to study transcription of viral RNA in these lines. We have developed cell-free RNA synthesis, using nuclei isolated by a non-aqueous method, to examine undegraded initial transcripts. We plan to use the method to examine SV40 synthesis in cell lines carrying the SV40 genome but expressing it in a variable manner. BIBLIOGRAPHIC REFERENCES: Gurney, T. Jr. and Foster, D. N. (1976). Non-aqueous isolation of nuclei from cultured cells. Methods in Cell Biology. Harmon, S. A. and Gurney, T. Jr. (1976). Products of cell-free RNA synthesis using conditions preventing initiation and processing. ICN-UCLA Symposium on Gene Expression.